title: [Study on the content and carbon isotopic composition of water dissolved inorganic carbon from rivers around Xi'an City].
abstract: In this study, the content and isotopic compositions of water dissolved inorganic carbon (DIC) from four typical rivers (Chanhe, Bahe, Laohe and Heihe) around Xi'an City were studied to trace the possible sources of DIC. The results of this study showed that the content of DIC in the four rivers varied from 0.34 to 5.66 mmol x L(-1) with an average value of 1.23 mmol x L(-1). In general, the content of DIC increased from the headstream to the river mouth. The delta13C(DIC) of four rivers ranged from -13.3 per thousand to -7.2 per thousand, with an average value of -10.1 per thousand. The delta13C(DIC) values of river water were all negative (average value of -12.6 per thousand) at the headstream of four rivers, but the delta13C(DIC) values of downstream water were more positive (with an average value of -9.4 per thousand). In addition, delta13C(DIC) of river water showed relatively negative values (the average value of delta13C(DIC) was -10.5 per thousand) near the estuary of the rivers. The variation of the DIC content and its carbon isotope suggested that the DIC sources of the rivers varied from the headstream to the river mouth. The negative delta13C(DIC) value indicated that the DIC may originate from the soil CO2 at the headstream of the rivers. On the other hand, the delta13C(DIC) values of river water at the middle and lower reaches of rivers were more positive, and it showed that soil CO2 produced by respiration of the C4 plants (like corn) and soil carbonates with positive delta13C values may be imported into river water. Meanwhile, the input of pollutants with low delta13C(DIC) values may result in a decrease of delta13C(DIC) values in the rivers. The study indicated that the DIC content and carbon isotope may be used to trace the sources of DIC in rivers around Xi'an City. Our study may provide some basic information for tracing the sources of DIC of rivers in the small watershed area in the Loess Plateau of China.
authors.affiliation: State Key Laboratory of Loess and Quaternary, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710075, China. guowei@ieecas.cn
authors.forename: Wei
authors.initials: W
authors.lastname: Guo
authors.forename: Xiang-Zhong
authors.initials: XZ
authors.lastname: Li
authors.forename: Wei-Guo
authors.initials: WG
authors.lastname: Liu
mesh_terms: D002244:Carbon / Q000032:analysis*; D002247:Carbon Isotopes / Q000032:analysis*; D002681:China; D002947:Cities; D004784:Environmental Monitoring; D005618:Fresh Water / Q000737:chemistry*; D007287:Inorganic Chemicals / Q000032:analysis*; D045483:Rivers / Q000737:chemistry; D012995:Solubility
chemical_list: D002247:Carbon Isotopes; D007287:Inorganic Chemicals; D002244:Carbon